Up-scaling laboratory set-ups for water flow and solute transport in unsaturated soils: from column tests to laboratory lysimeter

Tracer tests in laboratory columns have been widely used, both in saturated and unsaturated conditions, to study the infiltration in soil and subsoil. The columns used for laboratory research, during the years, varies in dimensions and characteristics but in literature, it is possible to find very few studies in which laboratory lysimeters are used. In this thesis, laboratory tracer tests have been performed at three different scales (small and intermediate column, and laboratory lysimeter). In the small scale, saturated and unsaturated tests have been performed while, with the intermediate column and the lysimeter, only unsaturated tests have been done. The main aim was to investigate the differences between the scales in terms of operating conditions, dispersivity value and hydraulic conductivity. Furthermore, with a particular focus, the set-up and data of the lysimeter have been studied. The results obtained from the experiment shown that there is no substantial variation in the hydraulic conductivity values between the scales while a very little variation can be observed on the dispersivity value, as it increases as the column length increases. Interesting data have been obtained also from the lysimeter’s tensiometers, which have shown an anomalous behaviour in the first part of the sand column. This phenomenon can be caused by a non-homogenous flux in the first part of the column, but further studies could be performed to deeper investigate this behaviour. The lysimeter proved to be a very useful device for studying the vadose zone. In comparison to the other scales, its high precision sensors allow to study with a great detail the phenomena occurring within the unsaturated zone. This thesis can be considered a good starting point, from which new studies, regarding infiltration of contaminants and water flow in the vadose layer, can be undertaken.